This invention relates to a cutout module for a vehicle starting circuit. It is applicable to any vehicle ignition system but is particularly useful in vehicles having a heavy duty cycle for the ignition switch. Service and delivery vehicles are likely to have such a heavy duty cycle because the vehicles are started and stopped so frequently. A particular example of this is the long life vehicle (LLV) used by the United States Postal Service.
The LLV has an ignition switch with a contact rating of 35,000 cycles. The amperage rating is approximately 30 amps. The switch design consists of spring contact terminals and a drag plunger spring resistor. Due to the extreme duty cycle of the LLV (some starting up to 250 times a day) the ignition switch may reach its designed cycle threshold in under one year. Accordingly, these vehicles have been subject to ignition switch failures, apparently due to mechanical wear of the ramps and/or contact bars within the switches. Switch failure can cause carbonized shorting within the switch. It is believed that such shorting has been the cause of several vehicle fires.
One way to address the problem of ignition switch failures is to replace the switches as part of routine maintenance. But this approach has proven to be extremely costly. Another problem with routine replacement of the ignition switches is that studies to date have not been able to positively identify the exact failure mode or the predicted time at which a switch can be expected to fail. Thus, replacing ignition switches on a routine basis may result in replacement of switches that have significant remaining life. Conversely, some switches may fail and cause fires well before their rated life cycle expires.